The sound of four gunshots soon after a man and a Suffolk police officer chasing him disappeared from view was a bad sign one night last March in Huntington Station, the officer’s two partners testified Tuesday in Riverhead.

Within seconds, they found out how bad when they found Officer Mark Collins bleeding from his neck in a driveway on Mercer Court. Collins had been running after Sheldon Leftenant, 23, who is now on trial, charged with the attempted aggravated murder of Collins.

On a police radio recording played for the jury, Collins shouted “10-1! 10-1! 10-1! 10-1!” — code for an officer in need of assistance. One of Collins’ partners, Officer Damian Torres, told the other, Officer Robert Dorr, “Mark’s been shot,” Dorr testified.

“I knelt down to Mark and I told him, ‘You’re going to be OK,’ ” Dorr testified during questioning by Assistant District Attorney Robert Biancavilla. “He stated, ‘Sheldon Leftenant shot me.’ ”

Collins will testify later in the trial. About a dozen patrol officers, District Attorney Thomas Spota and Det. Nicholas Guerrero, who barely survived being run over at an unrelated traffic stop, watched testimony Tuesday.

The three plainclothes officers had followed a speeding car east on Jericho Turnpike and pulled it over on Goeller Avenue. Almost immediately, the officers were on alert because the backseat passengers, Leftenant and Robert Primm, would not keep their hands in sight. Dorr said he and Collins knew both men.

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Dorr said he ordered Primm out of the car. Leftenant gave his learner permit to Collins but then took off running.

Collins followed right behind, and then Dorr and Torres ran too, they said. Leftenant ran across Jericho Turnpike, went one block west to Mercer Court and then up a driveway.

In his opening statement to jurors, Biancavilla said Collins fired his Taser at Leftenant, but it had no effect because the probes could not penetrate Leftenant’s winter jacket. So Collins tried to tackle Leftenant, Biancavilla said.

“All of a sudden, all Officer Collins saw were flashes, and he couldn’t move his right side,” Biancavilla said.

K-9 unit officers testified Tuesday that their dogs tracked Leftenant to a storage shed on the next block within an hour. When he was found, Biancavilla said, the Taser probes were still stuck in his jacket.

Defense attorney Ian Fitzgerald conceded that his client shot Collins, but said the evidence doesn’t support the charge against Leftenant.

“The official version is not what happened,” Fitzgerald said. He told jurors that after Leftenant was chased by men in plain clothes driving an unmarked car, it may not have been clear to Leftenant that he was dealing with police.

But Dorr and Torres said they wore bulletproof vests with the word “Police” on it. They said Collins had a jacket on, but it was unzipped and his vest was visible.

Before the trial started, Fitzgerald told state Supreme Court Justice John Collins (no relation to the officer) that prosecutors improperly withheld evidence by failing to turn over surveillance video showing the officers chasing Leftenant until after jury selection was complete. Fitzgerald said if he had known of that video months ago, he might have altered his pretrial and trial strategies.

Biancavilla said police gave him the video just last week, but he did not know why police waited 10 months to do so.

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Fitzgerald asked that the video be suppressed. Justice Collins said he would rule on the issue Wednesday.