The police in Sri Lanka say one of their officers has been shot by a suspected Tamil Tiger rebel.
The Tigers have been blamed for a number of recent killings
The gunman then tried to swallow a cyanide tablet after the police caught him.
Officials say the manner of the attack resembles a series of recent killings blamed on the Tamil Tigers.
The Tigers and the government have been observing a ceasefire for more than one year, but the rebels are currently refusing to attend peace talks.
Police say the gunman walked into a police station near the centre of the capital Colombo on Monday.
He then shot the officer, Inspector Nihal Thabrew, in the head while he was asleep.
Inspector Thabrew was a member of an anti-terrorism unit.
Reuters news agency quotes police spokesman Rienzie Perera as saying that the gunman had been a police informant.
"It was an informant turned double agent who killed the inspector of police," officer Perera said.
"The informant used to come to the police station and was seen in the morning before the shooting."
The gunman fled the scene but the police managed to catch up with him.
They say he then swallowed a cyanide tablet, a trademark move of the Tamil Tigers to avoid capture by the security forces.
Police say the man is critically ill.
In spite of the ceasefire, the Tamil Tigers have been accused of killing more than 30 people in recent months. The victims are either rival Tamil politicians or members of the intelligence services.
The Tigers are refusing to rejoin peace talks until they receive guarantees over their demands for power-sharing in the north-east of Sri Lanka.