Thirty-three minutes after he sprayed the Pulse nightclub with bullets, Omar Mateen, in a calm and measured 911 call to police, pledged allegiance to the self-proclaimed caliph of the Islamic State, invoked “God the Merciful” in Arabic and boasted of the massacre he had begun, records show.

The 29-year-old terrorist, whose rampage left 49 people dead and 53 injured before he was shot dead by police who stormed the nightclub starting at 2:02 a.m. on June 12, had also called for the United States to end its bombing campaign against the Islamic State in Syria and Iraq, where thousands of foreign fighters have flocked to help overthrow Syrian President Bashar Assad.

Transcripts of the four conversations Mateen had amid what has been called the country’s worst mass shooting are providing new insights into the motivation of a man whom federal authorities had watched for several months but never prosecuted for his sympathies with terrorist groups or hatred for gays.

See alsoOrlando one week laterEditorialEditorial: Many holes in security against mass killersMore coverageOrlando nightclub shooting

Mateen had also posted items on Facebook, scoured the web for news of reactions to the atrocity he was carrying out and exchanged texts with his wife, Noor Salman, as victims scrambled for cover, nursed wounds or lay dead as the shooting unfolded, officials have said.

Portions of the transcripts were released Monday by the FBI as questions arise over whether Salman, who knew of the impending attack and tried to dissuade Mateen from carrying it out, was fully aware of the consequences of her and her husband’s actions.

Orlando Regional Medical Center, which treated 44 of the 53 injured victims, said Monday that of the 18 people who are still under its care, four are in critical condition and 14 are in stable condition. Three more surgeries were scheduled for Monday. At nearby Florida Hospital Orlando, where 12 shooting victims were taken, three remain, all in fair condition, a hospital spokeswoman said by email.

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Mateen’s first 50-second call to police began about 2:35 a.m., when Mateen announced, in Arabic, “In the name of God the Merciful, the beneficent,” to which a dispatcher replied, “What?”

Mateen replied: “Praise be to God, and prayers as well as peace be upon the prophet of God” in Arabic but switched to English, saying “I wanna let you know, I’m in Orlando and I did the shootings.”

He continued: “My name is I pledge of allegiance to Abu Bakr al-Baghdadi of the Islamic State.” Abu Bakr al-Baghdadi is the self-proclaimed caliph of the Islamic State, which has designated as its caliphate an area straddling the border between Iraq and Syria. The group of Sunni Muslims seized the territory in the midst of Syria’s 5-year-old civil war, in which it seeks to overthrow the mainly Shia government of Bashar Assad as well as the mainly Shia government of Iraq, which is backed by the United States.

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In its summary of the conversations, released Monday, FBI officials said:

“In these calls, the shooter, who identified himself as an Islamic soldier, told the crisis negotiator that he was the person who pledged his allegiance to [omitted], and told the negotiator to tell America to stop bombing Syria and Iraq and that is why he was ‘out here right now.’ ”

The summary went further: “When the crisis negotiator asked the shooter what he had done, the shooter stated, ‘No, you already know what I did.’ The shooter continued, stating, ‘There is some vehicle outside that has some bombs, just to let you know. You people are gonna get it, and I’m gonna ignite it if they try to do anything stupid.’ ”

It continued: “Later in the call with the crisis negotiator, the shooter stated that he had a vest, and further described it as the kind they ‘used in France.’ The shooter later stated, ‘In the next few days, you’re going to see more of this type of action going on.’ The shooter hung up and multiple attempts to get in touch with him were unsuccessful.”

The final call started at 3:24 a.m. and lasted three minutes, the FBI said.

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After that, Orlando’s police officers and SWAT team rescued victims by removing an air conditioning unit from a window and blowing up a wall, driving an armored vehicle through it to get to Mateen, who was reported dead after a firefight with police about 5:15 a.m.

As the city of Orlando and nation mourn one week after the shootings, officials have begun considering filing charges against the killer’s wife. But new information about her mental competence is affecting their decision to implicate her in the massacre, sources said.

Salman, 30, of Fort Pierce, Florida, had attended special education classes as a child and struggles to comprehend information — factors that could impact attempts by prosecutors to prove she committed a crime by keeping her husband’s attack plans secret, a federal law enforcement source has said.

She is being investigated by the FBI and federal prosecutors to determine whether she knew her husband planned to carry out the June 12 attack and failed to report it to authorities, the source said.

Salman had given Mateen a ride to Pulse nightclub several days before the shooting, apparently to scope out the level of security there. She also accompanied him to buy ammunition, the source said.

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On several occasions, Salman pleaded with him not to carry out an attack, the source added.

A grand jury has been convened to hear evidence in the case, and will likely weigh charges against Salman that could range from abetting a crime to conspiracy to commit an act of terrorism, the source said.

Yet the source acknowledged prosecutors’ decisions could be complicated by what he called her “comprehension issues.” She struggled in school while growing up in California, the source said.

In a statement issued to ABC News, which first reported Salman’s academic struggles, her family said: “Noor is completely innocent and [was] unaware of the attacks,” adding she doesn’t understand “cause and effect.”

Earlier this week, Salman’s aunt, Mona Salman, who lives in the West Bank, told the Los Angeles Times: “Noor is a simpleton. Things happen around her and she is not aware of it.”

The family could not be reached for comment Sunday.

The daughter of Palestinian immigrants, Salman was born and raised in California. She met Mateen online and married him in 2011, the source said. The couple has a 3-year-old son together.