British detectives questioning a 19-year-old Norwegian of Somali origin over Wednesday night’s stabbing spree in London said on Thursday that they had found no evidence of terror motives or radicalization, AFP reported.

Assistant commissioner Mark Rowley told reporters the one woman killed in the attack in central London’s Russell Square late on Wednesday was a U.S. national. Police said earlier that she was thought to be in her 60s.

Among the two women and three men also injured were American, British, and Australian nationals, as well as one Israeli woman who was listed in light condition.

Three of the five have been discharged from hospital and the other two are not in a life-threatening condition, according to AFP.

The investigation “increasingly points to this tragic incident as having been triggered by mental health issues,” Rowley said outside London’s New Scotland Yard police headquarters.

“We believe this was a spontaneous attack and the victims had been selected at random,” he added, saying police had “found no evidence of radicalization or anything that would suggest the man in our custody was motivated by terrorism.”

Police had initially confirmed the attacker suffers from mental issues but also did not rule the possibility that the attack was terror-related.

Rowley said police work so far does not suggest that the suspect’s Norwegian nationality and Somali ancestry “are relevant to the motivation for his actions”.

He said an address had been searched in north London, while another in south London would be searched.

Rowley called it a “horrific murder and attack” adding Scotland Yard is in contact with the relevant embassies.

He said the suspect was shot with an electric shock gun and detained by armed officers within six minutes of the first call to the emergency services.