Question about transferring ownership of a Smart Contract?

I was recently transferred ownership of a smart contract for a NFT project. Everything has been done. Artwork completed, etc. I have all of the metadata files, control of GitHub, etc.

My question is, now that I have control of smart contract – is it possible for the former Owner to gain control of it again? Do I need the seed phrase?

Just trying to cover my bases. The previous Owner had to step away for rl issues and can’t commit to the project anymore. He’s been very cooperative and have no reason to believe he’d do anything nefarious but we’re going to build this community up and the project will become a Blue Chip.

I have rl friends to ask as well but wanted to crowdsource at much information as possible.

Any guidance would be much appreciated.