The family's attorneys also announced a $25 million claim against the city of Wilmington and said they want the officer who fired the shots to face criminal charges.
Family friends said Sunday that they have many questions, and that this is uncharacteristic behavior from Franks, who is a retired firefighter of 19 years and a Marine veteran.
The New Jersey Attorney General's Office says the man killed fired shots at police before being shot and killed in the encounter with officers.
Officials have not said who fired the shots that struck the officers or whether Gardner was armed at the time.
The AG's office said 52-year-old Donald Gardner, who is also known as Donald Capriotti, died in the encounter with officers.
The suspect was identified as Nasire Best, 21, of Dundalk, Maryland.