"She wrote lines that stung & hummed. 13 years in her presence was happily humbling. #RIPMichelleMcNamara," Oswalt tweeted, along with a link to make a donation in her honor to 826LA, an organization that helps students strengthen their writing skills.
McNamara, who was known as a crime writer, and Oswalt share a daughter, 7-year-old Alice. McNamara and Oswalt, 47, were married in 2005.
McNamara founded the website True Crime Diary, and wrote and podcasted about true crime, and also appeared on the Investigation Discovery series A Crime to Remember. She said she was most interested in cases that weren't necessarily getting big headlines, and she started her website at Oswalt's suggestion.
"I'm drawn to cases that aren't so high profile, that are maybe even a little neglected, but which have enough evidence and clues that anyone with a will and an Internet connection can try to piece together the puzzle," she said in 2011. "That's exciting to me. It feels like the difference between looking forward or looking back."
At the time of her death, she was working on a book about a serial killer she dubbed The Golden State Killer, whom she wrote a series of pieces about in Los Angeles Magazine.