Charges against a 16-year-old youth accused of shooting a Riverside man in the head the night after the City Grill massacre are expected to be upgraded following the death of the victim late Thursday in Erie County Medical Center.

Spencer Cowart, 23, is the city’s 40th homicide victim of 2010.

Darryl Tarver of Echols Lane, in the city’s William-Jefferson neighborhood, had been arrested late Sunday on attempted murder and felony first-degree assault charges in the shooting.

Cowart was shot in the head with birdshot from a shotgun and possibly also a .22-caliber handgun about 11:30 p. m. Aug. 14, near 43 Sattler Ave. Cowart had been listed in critical condition before dying of the injuries in ECMC.

“The charges will likely be upgraded due to the death of the victim,” Dennis J. Richards, Buffalo Police chief of detectives, said Friday.

Tarver remained in custody Friday in Erie County Holding Center, pending further court action.

The fatal shooting occurred less than a day after the City Grill shootings, in which four people were killed and four others wounded outside the upscale downtown restaurant. Two other men were fatally shot the same weekend.

The motive for the fatal attack on Cowart was not known. Buffalo police said Cowart was apparently involved in an altercation when he was shot.

Cowart was struck in the head with birdshot fired from a shotgun. Police also recovered a .22-caliber revolver on a lawn near the crime scene, authorities said.

Additional details about Tarver were unavailable.

State corrections records show Cowart served part of a 1-to 3-year prison sentence on a 2006 felony reckless endangerment charge before his release in July 2008.

Cowart also was arrested July 10 on a misdemeanor charge of criminal possession of stolen property after Amherst police responded to a burglary in progress on Springville Avenue and stopped Cowart and Brandon Barron, 23, of Bissell Avenue, for questioning.

Both had property from a recent burglary on Eggert Road in Buffalo, according to reports. The disposition of that case was not immediately available.