Big Sean has claimed a mentally-unstable fan attempted to ''hit him off guard'' at a CD signing in New York last week.

The 28-year-old rapper came under fire last Friday (17.02.17) when his meet and greet in Queens was shut down but he has now explained that he had no choice but to cancel the gathering because someone had tried to hurt him.

Taking to his Twitter account, the 'Blessings' hitmaker wrote: ''some guy waited in line in the cold since 10am, bought my CD, when I signed his CD n shook his hand he TRIED to hit me off guard

''the dude was released from a mental hospital last week, has a long record of mental illness n was off his meds. Very serious issues

''He claimed he had wrote songs for Michael Jackson, Jay Z n was wit Birdman etc. I'm hoping he's getting the proper treatment he needs. (sic)''

The hip-hop star concluded by apologising to his fans for the cancellation.

He said: ''I wanted to keep the signing going but the store shut it down. Sorry it got ruined for the rest of the real fans (sic)''

Meanwhile, despite the trouble he's had since becoming famous, Sean - whose real name is Sean Michael Leonard Anderson - recently penned an open letter to his 18-year-old self in which he claims his career will unfold before he enters high school and has even set his sights on a future in the music industry.

He wrote: ''Dear Sean, Listen, I know you've spent your whole life trying to push back those telling you to not be so hard on yourself.

''Relax, come hang, chill more. You didn't listen to them then, and I doubt you're going to listen to me now, but I want to tell you this from the heart - our heart: There is more to your life than your future.

''You've been telling yourself that by 21 you have to be on, and at 22 you have to have a song on the radio. Rapping's been your job since before it was your job, before you were out of high school, before you faced the decisions that would change everything. That hustle will create your path for you and be a testament to the light you have to share. But it will leave you with a lot more to work on.''