Mark Warman, 43, and Daniel Warman, 18, ran on to the pitch while watching the Canaries suffer a 7-1 hammering in the League One encounter.
The two men - believed to be father and son - were photographed and appeared to throw season tickets towards Gunn, said witnesses.
Police said on Sunday that two men had been arrested and charged with "pitch encroachment".
But a police spokesman said that checks had shown the fans were not charged but had each been given a police caution.
Norwich, meanwhile, have confirmed they will carry out an independent inquiry into the incident which saw two fans confront Bryan Gunn during the defeat.
A statement said: "We take the safety of our supporters and staff very seriously.
"There will be a thorough independent inquiry into the safety measures which were in place and the incident involving the two men."
Source: Team_Talk