A 17-year-old boy was fatally shot on Tuesday during an argument over a water gun fight that broke out in a Bronx park on one of the hottest days in New York City in over a decade, the police and the boy’s mother said on Wednesday.

The boy, Darrell Harris, was shot at least twice, in the head and in the arm, and died of his injuries on Tuesday night, according to the police. The shooter and another man involved in the altercation — neither of whom have been identified by the authorities — fled the scene, according to a law enforcement official with knowledge of the incident.

No arrests have been made, the police said.

The fatal shooting inside a city park comes days into a sweltering heat wave, which has blanketed the region since Sunday evening, driving temperatures toward the triple digits.

The episode stemmed from an encounter at Starlight Park, beside the Bronx River, between Darrell and a group having a water gun fight, which suddenly turned violent, according to the law enforcement official.

Darrell and a few friends had gone to the park to take refuge from the heat, according to his mother, Kellie Lewis. There, they encountered a group of people having a water gun fight with gel blasters, toy guns that shoot dissolvable gel pellets instead of water, according to the official.

What began as a joyful summertime outing soon escalated into a bout of violence.

A man from the water gun group, who has not been identified by the police, began shooting the pellets at Darrell, who grew angry, the official said. Darrell confronted the man, and the two began to argue and then physically fight, while a group of onlookers formed around them, the official said. Then, in a flash, Darrell charged at the man, and another man from the water gun group drew a firearm and shot him.