Alexander Bischof, 37, from Fort Collins, Colorado, was visiting Germany when the shooting took place

The 37-year-old man accused of shooting a police officer in a Munich subway station on Tuesday is a US citizen born in Bavaria who was on a European trip, German officials said.

The suspect, identified as Alexander Bischof by family members, was a tourist from Fort Collins, Colorado, who was visiting Germany when the shooting took place.

Bischof is accused of shooting a 26-year-old policewoman in the head after stealing her colleague's gun at the Unterföhring station on the outskirts of Munich on Tuesday.

Despite family members saying that Bischof was the shooter, police have not confirmed the identity of the attacker in the assault, which left two bystanders also injured.

The suspect is in custody at a secure psychiatric unit and has since been charged with attempted murder.

Munich police chief Hubertus Andrae said that the suspect flew to Munich airport from Athens on Monday and spent the night in the airport.

Witnesses told police as the man rode the subway toward the city Tuesday he was talking to himself in English, then suddenly began punching another, apparently randomly chosen, passenger in the face, pummeling him until he was bloody.

Bischof is accused of shooting a 26-year-old policewoman in the head after stealing her colleague's gun at the Unterföhring station on the outskirts of Munich on Tuesday. Pictured above, policemen arrive on scene following the shooting

The suspect is in custody at a secure psychiatric unit and has since been charged with attempted murder. The 26-year-old police woman is fighting for her life after being shot in the head at the Munich station

Police were called and when the suspect got off at the suburban Unterfoehring station, two officers began questioning him.

Surveillance video shows one officer holding a pad of paper and pen taking notes when the suspect suddenly shoved him with 'extreme violence' toward an oncoming train, Andrae said.

In the ensuing struggle the suspect grabbed the officer's pistol from its holster, and opened fire at both of the officers.

He missed the officer whose weapon he took, but hit his 26-year-old colleague in her head as he emptied the eight-shot magazine.

Two bystanders were also injured, and are believed to have been hit by shots fired by the suspect.

The officer hit in the head appears to have fired at least one shot, hitting the suspect in the buttocks. Despite the wound, he was able to flee and was apprehended outside by other officers arriving on the scene.

Armed German policemen secure the scene of a shooting at the Unterfoehring subway station in Munich, Germany

Police officers secure the area around a commuter rail station in Unterfoehring near Munich, southern Germany, where shots were fired

A helicopter hovers above the scene which has seen one police officer and several others injured

The incident occurred this morning at Unterföhring station and German police said they had secured the area. Blood on the streets of Munich as a police officer is shot by a gunman at a train station

The injured officer was rushed to a nearby hospital and was still in life-threatening condition on Wednesday, Andrae said. She remained in critical condition on Thursday afternoon, according to The Local.

The bystanders who were injured by bullets were also treated and are stable.

Andrae said police had been in contact with the suspect's father with whom he had been living in the United States, and said the suspect apparently had a criminal record there.

He did not give further details but a police source confirmed German media reports that the suspect's name is Alexander B, and that he had been living in Colorado.

Bild newspaper reported he was staying in Fort Collins, but the source could not confirm that.

In addition to some 200 witnesses to interview, Andrae said police also have video surveillance footage from multiple locations to review and are still working on a complete picture of how the attack unfolded. The suspect has so far refused to talk with police.

The shooting occurred during a morning police check at the subway station as an armed officer stands guard

A police officer armed with a huge rifle walks the streets as the station is closed down for safety

Dozens of emergency vehicles descend upon the scene which has been cordoned off

Last July, an 18-year-old, David Ali Sonboly, shot dead nine people at a Munich shopping mall before turning the gun on himself, having spent a year planning the rampage.

Police said the German-Iranian teen was 'obsessed' with mass murderers such Norwegian right-wing fanatic Anders Behring Breivik and had no links to the Islamic State (IS) group.

And in March, an axe-wielding attacker wounded nine people in a bloody rampage at a railway station in the western city of Duesseldorf.

The 36-year-old Kosovan national had been diagnosed as a paranoid schizophrenic with a history of high anxiety and self-harm, police said, ruling out a terrorist motive.

Instead, they suggested he might have carried out the attack at the station to end his own life.

The suspect was taken into custody after jumping off a bridge.

German authorities have been on high alert since a series of attacks claimed by IS.

The most deadly came last December when a Tunisian rejected asylum seeker rammed a truck into a crowded Berlin Christmas market in an attack that killed 12 people and wounded dozens of others.

Armed German policemen secure the scene of a shooting at the Unterfoehring subway station in Munich