Darlene Horton, a 64-year-old American woman, died after being stabbed in London’s Russell Square Wednesday night. She was visiting London with her husband, a psychology professor. The attacker injured five other people, all but one of them now out of the hospital. There were some early reports that the attack might be terrorism but now authorities are saying that’s probably not the case. CNN reports:

Police said they had arrested a 19-year-old man on suspicion of murder. The suspect is a Norwegian national of Somali origin, and “so far we have found no evidence of radicalization,” London Metropolitan Police Assistant Commissioner Mark Rowley said Thursday…

Rowley said that authorities’ main line of inquiry was focusing on mental health issues, essentially ruling out terrorism as a likely motive.

Officials briefed on the investigation had earlier told CNN they believed the case was a terror attack based on the initial evidence.

“Whilst the investigation is not yet complete — all of the work that we have done so far, increasingly points to this tragic incident as having been triggered by mental health issues. At this time we believe this was a spontaneous attack and the victims were selected at random,” Rowley told journalists.

So maybe this is a case of mental illness and not a terrorist attack. But even CBS News says the entire city is on edge and police are saying it’s not a matter of if there will be another terror attack but a matter of when it will happen: