Andrew Heard, 69, set out to fish near Hinchinbrook Island on Thursday but didn't return, according to Queensland Police.
Investigators have since found human remains in the area and inside a 13.8-foot crocodile, police said Sunday.
The crocodile was caught and killed by the Queensland Department of Environment and Science (DES), which also killed a 10-foot crocodile as part of the investigation, the agency tweeted Monday.
"At this stage we can only confirm that we've found human remains in the first," Acting Inspector Andrew Cowie of Queensland Police said at a press conference Monday, explaining that the examination process has not been completed on the second crocodile.
Both animals were found in the area where Heard was believed to have been fishing, said Cowie, and the characteristics of the second crocodile are consistent with being involved in the incident.
"i believe that we've got the two crocodiles involved," he said.
Police found a small vessel with quite significant damage, said Cowie, who added that the investigation will now be passed on to the coroner.
"This is a tragic incident," he said, calling on people to be alert.
"It's very important that people are always aware of their circumstances," he said. "Anywhere in the north... if you're in the bush you have snakes and if you're on the water you have crocodiles."
Cowie underlined that people need to take precautions.
"Always make sure you tell people where you're going, always make sure you have appropriate safety equipment, always make sure you're able to get to that safety equipment, if you need to, in a hurry," he said. "Please be very careful."
Another fisherman told CNN affiliate 7News of his run-in with a large crocodile in the same area where Heard went missing.
"He would have been the length of my boat," Luke Nation told 7NEWS, adding that the 15-foot crocodile had bumped the hull of his vessel. "It scared us. He definitely was giving us our marching orders, I think."
This is the third crocodile attack in Queensland this month, according to 7News, after swimmers in Cairns and Weipa survived their encounters.
Crocodile attacks are rare in Australia, but Queensland officials run a public safety campaign to alert residents to the risks of swimming or relaxing near croc-infested waters.
At the end of January a man escaped from a crocodile that had bitten his head by prizing open its jaws with his bare hands. The 44-year-old Queensland man fought off the creature while swimming at Lake Placid, near Cairns.
In 2019, a Queensland fisherman narrowly escaped an attack by poking a crocodile in the eye.
In September 2020, a massive 14-foot crocodile was captured at a tourist spot in neighboring Northern Territory.