It's time to say goodbye to a legend. Merle Haggard passed away on Wednesday, April 6, his birthday, at the age of 79.

Haggard's agent tells CNN that the country star lost a prolonged battle with pneumonia. In late March, these ongoing health issues forced him to cancel several tour dates with Willie Nelson, including a highly anticipated three-day stint in New Braunfels, scheduled for April 15 to 17.

The California native left an early life of crime and became one of the biggest names in outlaw country music. Haggard's name is synonymous with the "Bakersfield sound" — and hits like "Mama Tried" and "Okie from Muskogee."

His most recent project, a duet album with longtime friend and collaborator Nelson, was recorded at Austin's renowned Arlyn Studios. Django and Jimmie debuted at No. 1 on Billboard's country chart last year. In November 2015, he played a memorable show at Austin's beloved Nutty Brown Cafe.

Ryan Bingham, Jamey Johnson, and Shakey Graves have been added to the lineup for Nelson's upcoming show at Whitewater Amphitheater. And they have big shoes to fill. Of Haggard, Nelson tells TMZ, "He was my brother, my friend. I will miss him."