Alistair Bell was jailed for nine-and-a-half years in 1997 for his part in a ruthless drugs business.
Bell, 42, shot an unarmed 29-year-old officer, who escaped with severe bruising near to his kidney area after a bullet lodged in his body armour, during the incident in the early hours of Tuesday morning.
Bell later fired a number of shots during the stand-off before he was killed. A nearby resident has claimed three bullets hit his house.
The Independent Police Complaints Commission has said forensic tests were delayed at Bell's home in Huddersfield, because of fears that the premises contained explosives.
Several floral tributes have been laid outside the property in Cockley Hill Lane, Kirkheaton. One of them referred to him as a "truly nice bloke".
Yesterday police officers remained outside the home as the inquiry, which is expected to take up to six months, continued.
Questions have now also been asked as to why unarmed officers were sent to the address given Bell's violent history which included a conviction for possession of a shotgun with intent to cause fear.