The man who manufactured a bomb and detonated it at a kindergarten in eastern China on Thursday, killing at least 7 and injuring 65 others, suffered from neurological disorders, officials said on Friday, according to Reuters.

According to the officials, the 22-year-old man, surnamed “Xu,” who was also killed in the blast, had words for death scribbled on the walls of his home.

The Xinhua news agency said police were considering the act a "criminal offense” despite the perpetrator's mental issues.

According to China Central Television, Xu had dropped out of school due to his neurological condition and had been renting an apartment near the kindergarten.

"Self-made explosive device materials were found in his apartment, and on the walls in many places were handwritten words such as kill, death, destroy and terminate," it said.