A former Marine who law enforcement sources say was taken into custody on the subway in Brooklyn after police found he was carrying a duffel bag containing a shotgun, a cache of ammunition, a laser and a machete is mentally ill, his mother tells NBC 4 New York.

The 27-year-old man's mother said Wednesday that her son feels responsible for protecting New Yorkers and is burdened by guilt that he let 9/11 happen. She says he has a history of mental illness.

Police were called after witnesses reported seeing the man on the S53 bus in Bay Ridge at about noon with some kind of weapon sticking out of a bag, according to law enforcement sources.

By the time police arrived, he'd already gotten off the bus, the sources said.

Officers canvassed the neighborhood and located the man waiting for a Manhattan-bound R train close to the bus stop. Police approached him and asked to check his bag.

Police found an unloaded shotgun, shells for the gun, various machine gun and handgun magazines, a military radio, a laser for a shotgun, a machete and a Marine Corps uniform.

Law enforcement sources say that the weapons were all property of the US Marine Corps.

When asked if he had permits for the weapons in his bag, he said he did not need permits, according to the sources. He told police it was not his intention to hurt anyone.

The man agreed to go with the officers to the 68th Precinct station. He's expected to be charged with criminal possession of a weapon, the sources said.

His mother said he served three tours in Iraq. She said he is very kind and is not violent.