6:48 AM PT -- A rep for the Ronald Reagan Presidential Foundation and Institute tells TMZ they're "both saddened and concerned" about Hinckley's conditional release and music career. They said they "strongly oppose his release into society where he apparently seeks to make a profit from his infamy."
John Hinckley -- the man who tried killing Ronald Reagan once upon a time -- has turned a new leaf in the world of music ... and it sounds like he can get asses in the seats.
The one-time, would-be presidential assassin -- who shot Reagan in 1981 but was subsequently acquitted by reason of insanity -- has an upcoming performance in Brooklyn this summer that has apparently sold out in tickets ... this according to the venue itself.
The place is called the Market Hotel, and per their website ... there are no more seats available for Hinckley's show on July 8, where he's booked to play the guitar and sing some songs.
The ticket prices were going for $20 a pop before they all got snapped up -- and BTW, this place has somewhat of a decent-sized capacity ... 450 people can fill the joint, so ya gotta imagine at least a few hundred heads are gonna be watching come showtime.
Hinckley has been all-in on this sing-songy occupation since he cashed in on his unconditional release earlier this year ... this following being sprung from a Virginia psych ward in 2016 and fighting for less and less supervision throughout the years.
The guy has about 26k subscribers on his YouTube channel ... and he's also penned/performed a handful of original songs while strumming his instrument.
Here's another wild aspect to this ... Hinckley says he's started a record label in the past few months, which he calls Emporia Records. The first release, he explains, will be a 14-track CD of his own original songs as well as covers.
Hinckley has invited others to hop on board and join him ... posting an address for folks to submit their music for consideration. We'll give him this -- he's as charismatic as they come.