Samuel Moreno-Carranza, age seven, was injured after his mother fired a rifle inside church and police responded, killing her

A boy who was shot in the head at celebrity pastor Joel Osteen’s Houston megachurch on 11 February has lost “a portion of his frontal lobe” while recovering at the hospital, according to his grandmother.

In a Facebook post three days after the shooting, Walli Carranza said her seven-year-old grandson, Samuel Moreno-Carranza, “has lost a major part of what makes us who we are” after “half of his right skull [had] to be surgically removed during two surgeries done in less than 24 hours”. Samuel had endured “cardiac arrest multiple times, and no one can determine whether he has significant brain activity because his scalp tissue is too friable” to let doctors attach electroencephalogram wires to him, Carranza added in a post that doubled as a criticism of the US’s lack of meaningful gun control.

“Samuel had no protection of his God-given right to life,” Carranza’s post also said. “Because the very same legislators who claim to be ‘pro-life’ [in the public debate about abortion] believe that unbridled gun rights matter and the right to life does not! Insanity!”

Carranza’s update on Facebook came as authorities continued trying to determine why Samuel’s mother, Genesse Moreno, stormed into Lakewood church and began firing a rifle styled after an AR-15.

The attack ended when a Houston police officer and an agent with the Texas alcoholic beverage commission shot Moreno to death. Samuel – whose mother had brought him to the church – was struck in the head during the exchange of gunfire that killed Moreno. A 57-year-old man was also hit, in the hip.