It is not the first time Mr Ellwood's life has been touched by an atrocity, as his brother Jonathan was killed in the 2002 Bali bombing.
Mr Ellwood, who was pictured with blood on his face and clothes as he battled to help the police officer, was quoted by The Sun as saying the Westminster incident was a "huge tragedy".
"I am a witness, I was the last one on the scene before he died so I am not allowed to say anything. Number 10 has been in touch so I'll get into trouble.
"It is now murder, I was on the scene and as soon as I realised what was going on I headed towards it.
"It is a huge tragedy, it really is.
"I tried to stem the flow of blood and give mouth to mouth while waiting for the medics to arrive but I think he had lost too much blood.
"He had multiple wounds, under the arm and in the back.
"As I understand it the attacker has also died.
"I'm not allowed to say anything, I'll get into trouble.
"It's very sad," the newspaper reported him saying.
Eyewitness Hugh Dickinson, a 21-year-old student from High Wycombe, posted a picture of Mr Ellwood on Twitter, showing the minister bleeding, but saying "he looked to be fine".
Mr Dickinson said: "He had blood on his forehead as you can see but he wasn't bleeding profusely.
"It looked like either a smear or graze and you can see some on his cuff too if you zoom in. He looked to be fine - no obvious limp or anything."
The Bournemouth East MP is Foreign Office Minister, with the Middle East, Africa and counter terrorism listed among the areas within his brief.