The father of the gunman who killed at least 39 people on a tourist-filled beach in Tunisia said Sunday he is “shocked” and “ashamed” by the violence his son unleashed Friday.

The suspected gunman – identified by Tunisia’s Interior Ministry as 24-year-old student Seifeddine Rezgui – died during the Friday attack after killing and injuring dozens of vacationers, most of whom were British, German and Belgian. At least 30 Britons died in the attack, NBC News has learned.

The assault was claimed by ISIS.

“I have no idea who influenced him or who put these ideas in his head,” Rezgui’s father, Hakim, told NBC News partner ITV News. “I am so shocked … I am so ashamed,” Rezgui said.

After hours of being questioned by police, Rezgui said he was grieving for the families of the 39 people who were killed. “I feel the loss of the families so strongly. I feel like I have died along with the victims,” he said.

Rezgui’s aunt, Zara, said the family didn’t know of his radicalism. “He told us nothing of his secret,” she told ITV. “God has cursed us.”

Three of Rezgui’s roommates and were also detained for questioning Sunday in connection with the assault, Interior Ministry spokesman Ali Aroui told The Associated Press. Aroui said that “we are sure that others helped but did not participate” except indirectly.

Mohamed Mijbary, who prays at the mosque next door to an apartment that Rezgui lived with six other students until about a month ago, said the suspected attacker was polite, but never stopped to talk.

“He kept to himself. He dressed normally. There was nothing to suggest he was an extremist, a radical,” Mijbary said.

He said some of the students Rezgui lived with were observant Muslims, while others were not, and he never saw Rezgui pray at the mosque. The site of the massacre, in front of the Imperial Marhaba Hotel, was guarded by extra security officers Sunday, while people left flowers and notes at a growing makeshift memorial in the still-bloodied sand.