KUALA LUMPUR, Dec 2 ― The police said today that the suspect who reportedly ran amok and shot four people on the Tun Dr Lim Chong Eu Expressway in Penang last night possesses military background.

The bodyguard who is in his late 30s, was also said to be "mentally ill”, although the police did not specify his illness.

"From initial investigation the suspect has a mental problem but has no prior criminal record,” Inspector-General of Police Tan Sri Khalid Abu Bakar was quoted saying by news portal Malaysiakini.

Khalid also reportedly said that a weapon owned by a security firm has been found on the crime scene.

He added that the suspect had a "carry and use” licence.

Three people were killed, and four injured during the incident yesterday.

Among those injured was RTM cameraman Mohamad Amirul Amin, 28, is now reportedly stable after he was shot in the chest.

Media reports describe the shooter as the bodyguard of Datuk Ong Teik Kwong, 32, who was among those killed.

Police arrested the shooter at 7.30 pm. The motive for the shooting has not been determined.

Another 32-year-old man who was reported to be in the same car as Ong during the shooting had been remanded for seven days to assist investigation, The Star reported.