The accident happened around 7:45 p.m. last Friday night at Broad and Master streets in North Philadelphia.
The off-duty officer was taking part in a motorcycle ride for peace with about 100 other members of the Midnight Run for Peace and Men United for a Better Philadelphia.
The group's aim is trying to stop the violence and drugs in the city.
"The off-duty officer was on his motorcycle going southbound on Broad Street at Master. A car made a left hand turn westbound on Master and the officer on his motorcycle struck that vehicle," Lt. Ray Evers said the night of the accident.
Merke, an officer in the 35th Police District, was rushed to Hahnemann Hospital in critical condition. According to a police statement, he succumbed to his injuries on Thursday.
Action New is told the 28-year-old had recently become a father.
Many of his fellow motorcycle club members kept vigil outside of the hospital the night of the crash, comforting one another and praying.
Merke has been a member of the Men United for a Better Philadelphia group since it was founded eight years ago. Over the years, they have organized rides involving hundreds of motorcycle riders through the most dangerous neighborhoods of Philadelphia.
"That's what this group does," Commissioner Ramsey said. "They go into some of the most crime infested areas and show their presence and try to get people to turn their lives around. They really have done a lot of good."