An alleged 21 July bomber took a burka from his mother-in-law to escape London in disguise because he feared police would shoot him, a court has heard.
Mr Omar said without the veil police would have found him "easily"
Yassin Omar, 26, from north London, has admitted setting off a device on the Tube, but says it was in protest at the Iraq war and not meant to be deadly.
He said he ran away after police killed Jean Charles de Menezes by mistake, fearing he would be shot too.
Six men deny conspiracy to murder and cause explosions in July 2005.
In his second day of giving evidence at Woolwich Crown Court, Mr Omar told the court that when his device was detonated it sounded like a champagne cork and some fellow passengers "thought it was a joke".
"Some of them, they looked alarmed. Some of the ladies, they panicked," he said.
"I felt quite bad - my intention was not to do that to people."
He added that the incident was timed before lunch when there were fewer people on the Tube, because he wanted to avoid a "stampede".
When he heard of the shooting of Mr Menezes he thought his co-defendant Hussain Osman had been killed, he went on.
He fled to Birmingham by coach, dressed in a long black burka - a garment that covers the face and body - and carrying a white handbag.
"I was very scared, I thought they would have shot me dead," he said.
"I realised that this thing had taken a wrong turn and now an innocent man had been shot."
Mr Omar said he took one of his mother-in-law's burkas because she "had lots of them", adding that without a veil the police would have found him easily.
He was arrested at a house by armed officers from West Midlands Police on 27 July.
The defendant said he was woken by "something like a robot making a lot of noise" and fled to the bathroom where he was found standing in the bath, fully clothed and wearing a rucksack.
"I realised that today might be my last. I was praying to Allah and thinking they are going to shoot me and I am not going to have a chance.
"I thought if I was wearing a bag they would have to think twice and ask what I had got in there - then I would have had a chance to explain."
Mr Omar claimed he was beaten by the officers and hit with a Taser stun gun during the arrest.
"It was the worst feeling," he said. "It was like someone putting electricity into me. They put the Taser on my head and my heart.
"I thought 'Because they cannot shoot me they are trying to electrocute me to death'."
Mr Omar and Mr Osman, 28, of no fixed address, are on trial with Muktar Said Ibrahim, 29, from Stoke Newington, north London, Ramzi Mohammed, 25, of North Kensington, west London, Adel Yahya, 24, of High Road, Tottenham, north London, and Manfo Kwaku Asiedu, 34, of no fixed address.