Gallerist NY reports speaking to friends of Mike Kelley who confirm the artist’s death at 58:

The artist had recently been selected for the 2012 Whitney Biennial, an exhibition that he has participated in seven times in the past. He had major one-person exhibitions at the Whitney Museum, the Los Angeles County Museum of Art and MUMOK, Vienna. […]

Mr. Kelley showed at New York’s Metro Pictures Gallery for two decades, from the early 1980s until the early 2000s, when he began showing with Gagosian. Reviewing his 1988 show at Metro Pictures, critic Peter Schjeldahl wrote, “He’s an artist’s artist for those artists–now in the making–who will matter to us in the ’90s.”

Mike Kelley Has Died (GalleristNY)