How do I become a camera man at professional sports events?

For live sports, camera operators and other crew are almost always freelance. Meaning you work a gig for a daily rate. Camera people I think are on the lower end of the tier. For many its fun, but its also fast paced and can be extremely stressful. You have to be able to embrace that. You have to be comfortable in always hustling for your next gig and trying to open doors to other production companies. You will seldom find staff people with saleries and benefits doing live sports. Also, your work ethic and reputation is everything. You will not get any jobs if you don't pull your weight or do your job flawlessly. I know this sounds rough, but its a niche career and tight circle of people, so your reputation will proceed you. Theres a reason why most sports productions by inlarge go on without a hitch.
I worked with a guy who did it. He did tape replay and camera. There was a game once in Toronto where the director was directing in french. Lets just say it was a rough NHL game for him. Not everyone's is like that though.
So first off, learn about broadcasting and get an in somewhere. Live sports will always need camera operators, but in other parts of broadcasting, at least in the studio the job has been replaced by robotic cameras. So you have to learn many jobs to make yourself valuable to a crew. Such as audio, chyron, video replay, editing, producing, technical directing, etc. These jobsare very niche. Expect early on to be doing the grunt work and paying your dues like running cables at venues. The days of being paid at the local tv station to do camera in the studio are long gone. The jobs that are out there in the production world, want multitaskers.
When it comes to camera operating, in the studio there's a skill and an art to it for sure, but with practice its not that hard. However telling a story with a camera and editing it together is a better way to set yourself apart from the rest.

It is helpful to study broadcasting at a college and make sure you do an internship with a local broadcast channel or production company. Many local cable stations also have internships for high school students.

The link below contains the path to be a cameraman. To be in such events you need to apply for a job in the media covering it.

http://study.com/articles/How_to_Be_a_TV_Cameraman_Career_Guide.html

My other advice is minoring in broadcast in school. Major in marketing,advertising, journalism, public relations, etc. Those degrees will serve you better long term and have wider application across your career. To do the various jobs in broadcasting, minor in the production classes to get you those skills. Or perhaps pursue a trade school like Specs Howard. Get interships wherever possible. Preferably places that allow you to get practical hands on experience. A great place to internship and look for job opprotuniites, is that most major sports team in large venues almost always have a production crew. They do the in house promos, graphics and videos for the various displays, and support various games. These are the few places where you can do sports related production and have stability in the job. But my understanding is the people who do the actual telecasts are almost always freelancers. A freelancer's life usually involves lots of traveling from gig to gig too.