Law enforcement officials have evidence that both Carlton Hipps and Ramone Williams fired fatal shots in the murder of Officer Robert Wilson III, prosecutors said Wednesday, adding that they were weighing whether to seek the death penalty in the case.

A preliminary hearing for the two men, scheduled for Wednesday, was delayed at the prosecution's request because the investigation is continuing.

Assistant District Attorney Brendan O'Malley said a daylong hearing is scheduled for May 20. Video from inside the GameStop store where Wilson was killed, plus testimony from a dozen witnesses, will be presented, he said.

"Both individuals fired shots that killed Officer Wilson," O'Malley said. "That absolutely will be proven."

On March 5, Wilson was inside the store at 21st Street and Lehigh Avenue as part of his regular patrol in the 22d District. While there, he wanted to purchase a video game for his son. Police say that witnesses told them the two defendants entered the store and began shooting when they saw the officer.

Police officials hailed Wilson, 30, as a hero for drawing the gunmen toward him and away from others inside the store.

An "in-depth investigation into the background" of Hipps and Williams has not been finished, Assistant District Attorney Brian Zarallo said. That could factor into the decision to pursue the death penalty.

"That's not a decision that is made lightly," Zarallo said. "Obviously there are a lot of considerations, and a great many of those factors are things we are analyzing and continuing to look into."

Hipps and Williams are brothers who lived in a two-story rowhouse in Brewerytown. Hipps, 30, spent five years in prison for robbing a liquor store with an illegal gun in 2004. He was released in 2009 and completed parole in September.

Williams, 25, had a record for assault, police said.

"I'm looking to hear the completeness of the evidence from the District Attorney's Office and then we'll go from there," said Andres Jalon, Williams' attorney. "I am an opponent to the death penalty, which is part of the reason why I'm in the case."

Michael Coard, Hipps' court-appointed attorney, offered his condolences to Wilson's family and called him "a real hero." The attorney noted there is considerable video and eyewitness testimony against Hipps, but maintained his client has a right to a trial. Hipps, who was shot in the leg by Wilson's partner, spent less than a week in the hospital before being transferred to jail.

Prosecutors said it was important to put an abundance of evidence on the record before trial. Videos from a nearby Rite Aid and body camera footage from a responding officer are among the evidence that could be shown in May.

"Under these circumstances," Zarallo said, "we feel it's important to make comprehensive record and to show the volume and depth of the evidence of the events that unfolded that day."