Paris started it. Sure, it was a citizen's arrest, but Romeo had a job to do, and was prepared to defend himself if he had to. He begs Paris to buzz off and leave him alone, but Paris won't.
Romeo told him not to.
The thing that led to Paris's death was the several inches of steel blade that Romeo pushed into him. Why Paris was there, and why Romeo was there, and why they were fighting, is the result of a series of events which, you will not be surprised to hear, started in Act 1 of the play.
It wasn't just the Montague's fault. It was the Capulet's fault too. Why? Because if they hadn't been fighting, Romeo and Juliet wouldn't have had the need to hide their love from their families, meaning Juliet wouldn't have been sent to marry Paris, leading to Juliet never having to take the poison and never leading to Romeo thinking she's dead and him killing himself and then Julit killing herself.
To put him next to his love (Juliet). He says, "If thou be merciful, open the tomb, lay me with Juliet". But he only asks this once he has been fatally wounded by Romeo. Romeo had no wish or intent to kill Paris but did after Paris attacked him.
No. After he kills him he says, "Let me peruse this face. Mercutio's kinsman, noble county Paris!" It's a surprise.
romeo fights Paris (where?) and Paris dies.
When Paris sees Romeo hanging around the Capulets' family crypt, he assumes because Romeo is a Montague that he is there to do something rude and indecent to the graves of the Capulets. He refuses to listen to one word Romeo offers in explanation and insists on fighting him. You know how they say "assume makes an ass of u and me"; well, it not only made Paris an ass, it made him dead.
Romeo wins. Paris dies.
Romeo stabs Paris in Act V, Scene III of Shakespeare's play "Romeo and Juliet," when he encounters Paris at Juliet's tomb. Paris believes Romeo is there to desecrate the tomb, and they engage in a heated confrontation, resulting in Romeo fatally stabbing Paris.
After Romeo injured Paris. Paris told him "Lay me in the tomb with Juliet". Romeo agrees and put him in the tomb with Juliet.
Paris suspects romeo is attempting to desecrate the tomb.
The script for Act 1 Scene 1 of Romeo and Juliet does not indicate that anyone dies. Of course a director might choose to have someone die to show that the situation is serious, but that would be beyond the requirements of the script.