RIO DE JANEIRO — A Brazilian television cameraman was pronounced brain dead by surgeons at a Rio de Janeiro hospital Monday, four days after a firework lit by a protester struck him in the head. His death, the first in Brazil this year due to protests that threaten to disrupt the World Cup soccer tournament beginning in June, underscores the unruliness and violence that have come to characterize the small, but continued rallies that began with a series of mass demonstrations last year. Santiago Ilídio Andrade, a 49-year-old cameraman for the Bandeirantes television network, was filming a protest over a hike in Rio's bus fares last Thursday when a protestor, as yet unidentified, lit a large bottle rocket that flew up from the ground and struck him. Photographs and video of the firework's deadly, albeit accidental, trajectory have filled the front pages of newspapers and prime time news coverage in the days since. The incident is prompting renewed discussion about the protests, the sometimes oppressive police tactics to contain them and whether violence so far could lead to worsening unrest. Over the weekend, police arrested a young man who in photographs was seen handing the firework to the protester who ignited it. The man, according to local media reports, said he did not know the other protestor, but recognized him from previous demonstrations. With World Cup games scheduled in Rio and eleven other cities, and a presidential election shortly afterward, Brazil's government is closely watching the protests and the disruption they could cause were they to grow larger or more violent. On Monday, President Dilma Rousseff ordered Brazil's federal police force to help Rio authorities investigate the Andrade episode. At least six Brazilians died during the unrest in 2013.