Surrounded by a throng of police officers and emergency personnel, Ellwood was seen crouching on the cobblestone street applying pressure to the bare, bloodied torso of the victim. The man the politician was trying to save was a police officer who died, a witness on the scene told CNN. The witness asked not to be named, citing details that are now under police investigation.
Authorities identified the deceased officer as Keith Palmer, 48, a 15-year veteran.
Press Association photojournalist Stefan Rousseau captured the moment.
A few yards away, another person was also receiving medical attention as law enforcement enveloped the premises. Armed police were called in to assist in the situation, which is being described by the British government as a "terrorist incident until we know otherwise."
Before his political career, Ellwood served in the British Army for five years
, leaving with the rank of captain.
At the scene, Ellwood's face was smeared with blood. Sadly, this is not the first time such an attack has marked his life. Ellwood's brother Jon died in the 2002 bombings in Bali
Wednesday's incident began when a car was driven over Westminster Bridge, hitting and injuring
a number of members of the public and three police officers.
The car then crashed near the parliament building and at least one man, armed with a knife, continued the attack by trying to enter parliament, authorities said. Three people were killed, including the police officer. At least 20 people were injured.
The man believed to be the attacker was fatally shot by police.
The emotion of those at the scene was palpable, even as details about casualties and the nature of the attack continued to roll in.
Ellwood's fellow MPs applauded his bravery, calling him "an absolute hero."
"Huge respect...for his heroic efforts today," tweeted Maria Caulfield
"I'm grateful to the police and proud of Tobias Ellwood," tweeted Tom Tugendhat
. "A good man helping another."
This story has been updated to reflect the latest number of fatalities from London Metropolitan Police.