data mining firm has found between 20 and 50 social media accounts active in baltimore on monday were also used in ferguson last summer .
link suggests the presence of ` professional protesters ' or anarchists who looking to take advantage of freddie gray 's death to incite more violence .
one account tweeted photos of gray 's funeral and used language anticipating monday 's violent clashes .
a 10 p.m. - 5 a.m. curfew has been imposed by the mayor of baltimore .