How to understand these two sentences
“I personally suffered and was attacked by gang members back in El Salvador, just for being gay,” he told msnbc by phone Tuesday, moments after being closed out of Rep. Bill Cassidy’s D.C. office. The Louisiana Republican, who opposed a comprehensive immigration bill that died in the House last session, was among a handful of lawmakers targeted by about 20 advocates during a protest for reform.
My questions:1. What does "being closed out of" mean here?
2. Is the "Louisiana Republican" referred to "Bill Cassidy" ?
3. What does" targeted be" here mean? How to understand " was among a handful of lawmakers targeted by about 20 advocates "?

Question

How to understand these two sentences
“I personally suffered and was attacked by gang members back in El Salvador, just for being gay,” he told msnbc by phone Tuesday, moments after being closed out of Rep. Bill Cassidy’s D.C. office. The Louisiana Republican, who opposed a comprehensive immigration bill that died in the House last session, was among a handful of lawmakers targeted by about 20 advocates during a protest for reform.
My questions:1. What does "being closed out of" mean here? 
                     2. Is the "Louisiana Republican" referred to "Bill Cassidy" ?
                     3. What does" targeted be" here mean? How to understand " was among a handful of lawmakers targeted by about 20 advocates "?

Answer

More context would be nice. Can you link the article you got this from? Even without it, I can explain with a high chance of success, I think.

1. "being closed out of" can mean that he was asked to leave the office or that he was never allowed to enter at all.

2. Bill Cassidy is the Louisiana Republican. Within the story, we can guess this because the first quote came from someone who said "back in El Salvador" which implies that he is from El Salvador, and likely not a Louisiana Republican based on that fact. Also, a quick search on the Internet showed me that Bill Cassidy is a Republican in Louisiana.

3. "targeted by" means that, because Bill Cassidy opposed the immigration reform, advocates for the reform (people who support it) have attacked Bill Cassidy for opposing it. "Attack" here does not mean physical. They have likely tried to generate negative publicity (to get the public to hate Cassidy).

I'm not sure who the person from El Salvador is because the bit you quoted doesn't include enough information about him.