It was 40 minutes of terror for passengers of the Jaipur-Mumbai Superfast Express on early Monday as RPF constable Chetan Singh went around coaches, firing from his automatic rifle. In all, he discharged 12 of the 20 bullets in it. Officials said Singh was “hot-headed and appeared to have lost his cool”. The trigger for the incident is still being investigated as are reports of him suffering a “mental health breakdown”.