COPS failed to trawl through Jake Davison’s online activity before giving back the gun he then used to kill five people.
Devon and Cornwall chief constable Shaun Sawyer admitted his force feared invading the 22-year-old’s privacy.
He said: “We take and return firearms on a not irregular basis when people have emotional crises or we receive reports from family members, then they can be returned.
“What we don’t do, because firearms licencing is a lawful thing, is trawl the internet looking at people’s lives. That’s an invasion of privacy.”
Davison’s pump action shotgun was handed back last month.
He shot dead five people, including his mother and three-year-old Sophie Martyn, and injured two others in Plymouth, Devon, on Thursday before killing himself.
Tory MP Tim Loughton called for more rigorous checks before guns are returned.
He said: “Surely, those must include scrutinising social media to get a full idea of the person’s background.
“It’s a matter of public record. It’s a misunderstanding of social media to suggest it would be invading their privacy.”
In one chilling post, Davison had revealed his obsession with the 1987 massacre in Hungerford, Berks.
He also liked hundreds of gun videos on YouTube.
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A pensioner confronted Mr Sawyer during a visit to Plymouth by Home Secretary Priti Patel.
Stewart Parfitt, 78, said: “Why did you give that bloke his gun back when he’s been a bloody lunatic for years?”
A vigil was held yesterday at a shrine to those who were killed.
Devon and Cornwall police did not respond to requests for a comment.
It’s a misunderstanding of social media to suggest it would be invading their privacy.
Tory MP Tim Loughton