The man charged with murder in the shooting death of an NYPD detective had his first hearing Friday, and another man is being questioned in the robbery that led to the friendly fire shooting, law enforcement sources said. 

Two senior law enforcement officials said the second man in custody may have been serving as a lookout in the cellphone store robbery earlier this week. Investigators are also looking to see if there was any past electronic communication linking the pair to at least one other previous holdup. 

The Detectives' Endowment Association said earlier Friday it was offering a $10,000 reward for information leading to the arrest and conviction of a second suspect.

Meanwhile, Christopher Ransom, 27, was arraigned via video teleconference from his hospital bed. He was ordered held without bail as prosecutors noted he had at least 10 prior misdemeanor arrests, six of which ended in convictions, and twice failed to show up for court hearings in the past.

Legal Aid defense attorneys for Ransom said he was shot eight times during the robbery shootout in Queens, including once in the leg and may lose use of his leg as a result. 

They said he had a fake gun during the robbery at the T-Mobile store in Richmond Hill Tuesday night and never fired any shots. The death of NYPD Det. Brian Simonsen was caused by friendly fire, one lawyer noted, asking why Ransom should be charged with murder when he didn't fire the shots that killed the detective. 

And if Ransom was trying to commit suicide, the lawyers noted, he would have intended the bullets to him, not another police officer. 

They asked that Ransom be put on suicide watch and protective custody, which the judge granted. 

Legal Aid said in a statement after the arraignment that the shooting was tragic but asked the public not to demonize Ransom.  

"Our immediate concern involves access to Mr. Ransom; and up until this afternoon, the NYPD had repeatedly denied Mr. Ransom’s family and his attorneys the opportunity to visit him, to counsel him, and to appraise his condition," the statement said. "His defense team has also been denied access to case evidence, including recordings of the incident, while the Department has leaked selective details and false information about Mr. Ransom to press, including the erroneous claim that he has a felony record."

Sgt. Matthew Gorman, the second NYPD officer hurt in the shooting, was continuing to recover at his Long Island home Friday. He'd left the hospital Thursday and returned to his home in Seaford, using crutches and accompanied by several people. 

Simonsen and Gorman were were working on an unrelated case in the area of the robbery Tuesday, but responded to the 911 call for the robbery because it was nearby. Also responding: six uniformed NYPD officers, authorities said. 

When they arrived and went into the store, they saw Ransom emerge from the back with the imitation gun -- he was pretending to fire it. NYPD service members fired a total of 42 rounds in 11 seconds at the scene. Simonsen, a married 19-year NYPD veteran, was hit once in the chest. He later died. Gorman was hit once in the leg. 

Simonsen wasn't wearing a bulletproof vest when he was hit, but the other uniformed officers at the scene were wearing vests.

Ransom was shot multiple times and taken to a local hospital, where he was listed in stable condition. He was charged Wednesday.

The NYPD is continuing to review Ransom's social media accounts, Monahan said. He has numerous previous arrests, including criminal impersonation, larceny and fraud.

Simonsen, who worked in the 102nd Precinct in Queens, loved the community he worked with, officials have said. He is survived by his wife and mother. 

"This was his life — he loved the 102nd," NYPD Chief of Department Terence Monahan said at a Wednesday news briefing. "Everyone knew Brian was the cop that you reached out to if there was a problem." 

A wake for Simonsen is scheduled for Monday, Feb. 18 from 7 to 9 p.m. and Tuesday, Feb. 19 from 2 to 4 and 7 to 9 p.m. at Saint Rosalie Roman Catholic Church in Hampton Bays. The funeral will be held at the same church on Wednesday, Feb. 20 at 10 a.m.