The father of a suspect killed by police gunfire alongside NYPD friendly fire cop Brian Mulkeen is planning to sue the city.

Antonio Williams, 27, was fatally shot Sept. 29 by officers in the Bronx who were trying to arrest him and believed he was carrying a gun.

During the fracas, which was caught on bodycam footage, Mulkeen and Williams can be seen grappling on the ground for some 30 seconds before another officer yelled “He’s reaching! He’s f–king reaching! He’s reaching for it!” — prompting police to open fire, killing both Williams and Mulkeen.

In a new court petition, Williams’ father, Shawn Williams, is asking a judge to force the city to turn over and keep safe evidence including bodycam footage, surveillance footage, 911 calls and other records, so he can build a case against the city.

“The respondents violated Mr. Williams’ rights and negligently caused his death on September 29, 2019,” the papers filed in Manhattan civil court allege.

The court documents claim that Antonio had been waiting for a cab near 1132 E. 229th Street and Laconia Avenue when cops — who “had no reasonable belief any criminal activity was taking place” — began yelling at him prompting Antonio to flee and sparking the altercation.

“We’ll review the lawsuit if one is filed,” a city Law Department spokesperson said.