The problem in your photos could be fire blight but it is hard to say without more evidence. Fire blight does cause selective dieback of twigs and leaves of plants in the Rosaceae family, like your pear. It is important to observe the dark green marks on the affected plant tissue as the bacteria penetrates and the cankers that develop on the dying stems to confirm fire blight. I do not see these things in your photos but you should examine the tree for these marks.

For more information on identifying and managing fire blight, refer to this fact sheet from  Missouri Botanical Garden. It has useful photos of what to look for. Note that some streptomycin resistant strains of fire blight have been found in New York State in recent years.