The Fourth of July weekend brought the city’s most concentrated explosion of gun violence this year, with 12 people shot — three fatally — in little more than five hours.

The bloody mayhem from Saturday night through Sunday morning also marked the third consecutive weekend in which a dozen or more people were struck by bullets since the summer started.

Shootings were reported in The Bronx, Brooklyn, Queens and Staten Island, where two people were slain in separate incidents.

A passerby found one of those victims, Devon Powell, 24, around 5 a.m. in the gutter in front of a bus stop on Arlington Place, where dried blood still stained the sidewalk and street hours later.

Powell suffered a head wound so grisly that cops couldn’t tell if he’d been shot, stabbed or beaten.

An autopsy later determined the cause of death was a gunshot wound to the head and neck, according to the Medical Examiner’s Office.

“He was a good kid. He never bothered anybody. He grew up around here,” said a local resident in his 20s who declined to give his name.

Neighbor Mario Garcia, 36, said Powell’s family visited the slaying scene around 8 a.m. while his body was still lying there, with one young man falling to his knees in the middle of the road.

“They started crying right away. They were destroyed,” Garcia said.

The dead also included Tamecca Haskins, 32, who was fatally shot around 2:25 a.m. in Brooklyn during an incident in which an unidentified man, 34, was also hit and critically injured.

Last weekend, 15 people were shot — including three who died — in less than 12 hours during incidents that stretched across all five boroughs.

Another 21 people were hit by bullets between June 20 and 22, with two dying in shootings at barbecues in The Bronx and Brooklyn.

As of June 30, shootings in the city were up 8 percent, with 521 incidents this year compared to 482 during the same period in 2013.

Updated NYPD statistics were expected to be released Monday.