Drummer Tonmi Lillman, known as 'Otus' in the Finnish heavy metal group Lordi, passed away yesterday (Feb. 14) at the age of 38. No cause of death has been revealed as of yet.

The full identity of Otus, in keeping with Lordi's policy, remained a secret until now. The band wears masks and all the members use stage names to keep their identities private.

Lordi issued the following statement to their fans via their official website:

Our dear friend and band mate, "Otus" Tonmi Lillman, has sadly passed away.

He will be greatly missed and we send our condolences to his family and friends.

Otus: we thank You from the bottom of our hearts for the short time we got to know you and spend with you together.

Rest in peace, friend.

Lillman had joined Lordi in 2010 after replacing previous drummer Kita, who apparently had been fired from the band for revealing his identity. In addition, Lillman had played drums for a number of other notable outfits, including Sinergy and To/Die/For. He was also part of the heavy metal parody band Kylähullut fronted by Children of Bodom's Alexi Laiho.

The drummer was also a talented studio engineer who worked with several heavy metal bands, as well as a gifted 3D graphic designer and music video editor.

Loudwire offers its deepest condolences to Tonmi Lillman's family and to the members of Lordi.

Watch Late Lordi Drummer 'Otus' Tonmi Lillman in This Promo Video